The present invention relates to an open-cell foam based on a melamine-formaldehyde condensation product, a polyurethane or a polyimide, which has been modified with hydrophobins, to a method of producing such foams, and to the use thereof for absorbing organic liquids, as leakage and bleeding protection for liquid stores and for liquid-liquid separation.
Open-cell, elastic foams based on melamine-formaldehyde resins, polyurethanes or polyimides are known in principle. By way of example, reference may be made to “Foamed Plastics”, in particular section “4.6 Foams from Melamine-Formaldehyde (MF) Resins” and “4.9 Polyimide (PI) Foams” and “Polyurethanes—7.1 Flexible Foams”, in each case in Ullmann's Encyclopedia of Industrial Chemistry, 7th Edition 2006, Electronic Release, Wiley-VCH, Weinheim, New York 2006. Production methods for such foams based on melamine-formaldehyde resins are disclosed, for example, in EP-A 17 672, EP-A 37 470 or WO 01/94436.
Open-cell, elastic foams based on melamine-formaldehyde resins are notable for a comparatively low density, good flame-resistance, and high high-temperature and low-temperature stability. They are suitable in particular for the thermal insulation of buildings, vehicles, pipelines or tanks, for noise insulation, and as insulating and shock-absorbing packaging material.
Untreated melamine-formaldehyde foams absorb both hydrophilic and hydrophobic liquids very rapidly. The absorption of water can have an adverse effect on the properties, for example an increase in the density or a deterioration in the thermal insulation effect.
DE-A 100 11 388 discloses an open-cell melamine resin foam whose cell structure has been coated with a fluoroalkyl ester. This reduces the ability of the melamine resin foam to absorb both water and oil.
It is known from EP-A 633 283 to reduce the water absorption of melamine-formaldehyde foams by coating the foam structure with a hydrophobic material, in particular with an aqueous emulsion of a silicone resin. In the examples, a foam with an apparent density of 11 kg/m3 is used which, in an additional process step, is coated with a hydrophobic agent and, after the treatment, has apparent densities between 72 kg/m3 and 120 kg/m3. The higher density is extremely disadvantageous for weight-sensitive applications, such as, for example, applications in vehicle construction, and in particular applications in aeroplane construction and in space travel.
Hydrophobins are small proteins of about 100 to 150 amino acids which occur in filamentous fungi, for example Schizophyllum commune. They generally have 8 cysteine units. Hydrophobins can be isolated from natural sources, but can also be obtained by means of genetic engineering methods, as disclosed, for example, by WO 2006/082251 or WO 2006/131564.
The prior art has proposed the use of hydrophobins for various applications.
WO 96/41882 proposes the use of hydrophobins as emulsifiers, thickeners, surface-active substances, for the hydrophilization of hydrophobic surfaces, for improving the water resistance of hydrophilic substrates, for producing oil-in-water emulsions or water-in-oil emulsions. Furthermore, pharmaceutical applications, such as the production of ointments or creams, and also cosmetic applications, such as skin protection or the production of hair shampoos or hair rinses, are proposed. EP 1 252 516 discloses the coating of various substrates with a solution comprising hydrophobins at a temperature of from 30 to 80° C. Furthermore, the use as demulsifier (WO 2006/103251), as vaporization retarder (WO 2006/128877) or soiling inhibitor (WO 2006/103215), for example, has been proposed.
The use of hydrophobins for modifying open-cell foams based on melamine-formaldehyde condensation products, polyurethanes or polyimides is hitherto still not known.